Dynamics of electronic excitations relaxation in hydrophilic colloidal CdS quantum dots in gelatin with involvement of localized states

Dynamics of the 1S_e–1S_3/2 exciton in colloidal CdS quantum dots with diameter of $3.1÷4.5\mathrm{nm}$ in gelatin with involvement of localized states was studied by means of femtosecond photoinduced absorption spectroscopy (pump–probe), thermally stimulated luminescence (TSL) observed under permanently excited luminescence. It was found that the bleaching band occurs in the energy region of exciton ground state under excitation by femtosecond laser pulses. The complex dynamics of bleaching recovery is caused by the capture of electron on localized states, found using TSL. The stochastic model describing the dynamics of bleaching recovery is discussed. It is shown that the low efficiency of exciton luminescence is caused by the rapid capture of holes by luminescence centers.